<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>

</body>
<script>
    var num = prompt("请输入一个数字?");
    var reg = /^([0-9]|[1-9][0-9]|[1-5]\d{2}|6[0-5]\d|66[0-6])$/;
    if (reg.test(num)) {
        alert(num + "满足在0-666");
    } else {
        alert(num + "不满足");
    }
</script>

</html>